LONDON — The chief of the International Atomic Energy Agency on Saturday expressed “serious concern” after Moscow accused Ukrainian forces of launching a drone attack on the Russian-occupied Zaporizhzhia Nuclear Power Plant in southern Ukraine — an allegation that Kyiv denied.

The incident would be the first drone attack within the ZNPP perimeter since April 2024, the IAEA said in a statement posted to X. Russian forces captured the site in the opening days of Moscow’s full-scale invasion of Ukraine in early 2022. The facility now sits around 30 miles from the closest portion of the front line.

“The IAEA has been informed by the ZNPP that a drone today struck a turbine building at the site, reportedly causing a hole in its wall,” the agency said in its statement.

IAEA Director General Rafael Grossi, the statement added, “expresses serious concern about the reported incident which would endanger both the seven indispensable pillars for ensuring nuclear safety during the conflict as well as the five concrete principles to protect the ZNPP, which clearly state that ‘there should be no attack of any kind from or against’ the plant.”

Grossi warned that “attacking nuclear sites is like playing with fire,” the IAEA wrote, adding that it requested “access to examine the affected turbine building first-hand.”

Ukraine’s Southern Defense Forces — a military grouping which oversees the southern front — denied the Russian allegation and accused Moscow of engaging in “nuclear terrorism.”

“The Russian Federation continues to use the Zaporizhzhia Nuclear Power Plant as a tool of nuclear blackmail and information provocations. Reports circulated by occupation-controlled resources claiming that Ukraine’s Defense Forces struck facilities at the ZNPP are another attempt to discredit Ukraine and conceal Russia’s own criminal actions,” the unit said in a statement.

“Ukrainian service members operate strictly within the norms of international humanitarian law and fully understand the consequences of any actions involving nuclear facilities,” it added.

“It is Russia that has illegally occupied and militarily controlled the ZNPP since March 2022, turning a civilian nuclear facility into an element of military infrastructure. Russian forces violate restrictions on the deployment of military assets within the 5-kilometer zone around the plant, placing electronic warfare systems, weapons, military equipment and personnel on its territory,” the force continued.

The Southern Defense Forces said in its statement that Russia had not published “high-quality photos or videos allegedly showing the consequences of the strike” and said that Ukrainian forces do not possess the drones “necessary to create the kind of damage described by the Russian side.”

Ukraine’s Foreign Ministry, meanwhile, issued a statement describing the Russian reports as “baseless accusations.”

ABC News’ Tanya Stukalova, Oleksiy Pshemyskiy and Rashid Haddou-Riffi contributed to this report.